Volatiles and Fluids in Subduction Zones

Overview Theme B3

The key issue of subproject B3 is to understand control parameters of forearc fluid discharge and the fate of advecting volatiles in different subduction zone settings. Methodical cornerstones are (1) the estimation of volatile fluxes, in particular methane, from the seafloor to the water column, (2) the determination of turnover rates of reduced compounds, such as methane and sulphide, at the sediment-water interface, and (3) the investigations of geochemical and biological parameters effecting the efficiency of the benthic methane filter. The gained data will improve global estimates on benthic methane fluxes and emissions of methane from the ocean floor into the atmosphere.

The third phase of the SFB will concentrate on the compilation of existing data and comparisons with other active margin settings as well as on finalizing and novel field work off Costa Rica and Chile, respectively. Additionally, long-term mesocosm studies with sediments from fluid discharge areas are envisioned to study control parameters of the benthic methane filter under predefined conditions. Data gained from field work and in-vitro studies will be used in numeric models to assess the impact of transport processes on biomass distributions, microbial turnover and methane release fluxes from the seafloor. In summary, our subproject will combine different modern methods including in-situ, ex-situ, in-vitro techniques as well as numeric modelling to investigate the fate of methane from different perspectives and to fill gaps in the global methane budget.

Fig. A: Scheme illustrating the transfer of inorganic substrates, which fuel the benthic methane filter and the ecological habitat of cold seeps.